Mesh seams practical advice
There isn't one good method for unwrapping an object, it needs some experience, here are the steps I would do:
Make sure it doesn't have a UV map, Seams usually do not get shared by different programs, so sometimes they do have a UV Layout, just no seems. Make sure that's not the case.
Don't create additional Vertices (Knife tool)
Worth a shot: in Edit Mode hit U and choose smart UV project. It will probably create a lot of small islands though, which might not be what you want.
In edit mode select everything and hit ALT J. That gets rid of as many triangles as Blender  can do. If you're lucky, now you can use ALT click on edges to select loops and turn them into seams.
Try to hide the seams (less visible places on your object), because that's were texture artefacts can occur. It's not super important when you're drawing yourself, but it's a good practice none the less.
Create as big islands as possible without distortion/overlapping.